Automatic pilot



Jan. 30, 1951 o. E. EsvAl. ET AL AUTOMATIC PILOT 3 Sheets-Sheet l Filed Feb. 3, 1944 V JQ, Si Ilm-f E m w O- mi WMA .n N L I4 M OCY Jan' 30, 1951 O. E. EsvAL ET AL 2,539,411

AUTOMATIC PILOT Filed Feb. 3, 1944 5 Sheets-Sheet 2 www lll-Ilm INVENTORS ORL AIA/D E. ESI/,4L CAQ; FR/Scf/E Jan. 30, 1951 o. E. EsvAL ET AL AUTOMATIC PILOT 3 Sheets-Shea?l 5 Filed Reb. 5, 1944 Patented Jan. 30, 11951 AUTOMATIC PILOT Orland E. Esval, Huntington, and `Carl A. Frische, Great Neck, N. Y., assignors to The Sperry Corporation, a corporation of Delaware Application February 3, 1944, Serial N o. 520,842

14 Claims.

Our invention more particularly relates to an automatic pilot for dirigible craft in which a directional gyroscope is employed to provide a directional reference in azimuth for craft-controlling purposes and in which a flux valve is employed to slave the gyro. The present application is a continuation-in-part of our copending application Serial No. 366,370, led in the U. S. Patent Oii'ice on or about the 20th of November, 1940 and which matured into Patent No. 2,357,319.

It is an object of our invention to provide an automatic pilot for use primarily in controlling the course of a dirigible craft, which pilot comprises a directional gyro which is slaved by jmeans of a ilux valve of the character which continuously provides a signal voltage output,v

said signal voltages being employed to control the precessing means of the gyroscope in such a manner that the gyro will substantially continuously provide a correct, predetermined azimuthal directional reference, and said pilot including compensating means whereby turning movements of the flux valve with the craft will not eiect precession of the gyro unless the gyro has wandered from its azimuthal position.

Another object of our invention resides in providing an automatic pilot for a dirigible craft comprising a directional gyro and a flux valve of the character having a null output position for slaving the gyro to a predetermined directional reference. In this type of' pilot, wandering of the gyro will be reflected in a change in heading of the craft which will thereby move the flux valve to a signal output position causing procession of the gyro back to the position thereof from which it wandered. Hence, in a pilot of this character, the flux valve output may be connected directly in controlling relation to the gyro-processing torque motor of the gyro.

Another object resides in providing an automatic pilot of the foregoing characters including means for removing the flux valve control over the gyro during turning movements of the valve whereby to prevent incorrect gyro-procession due to turning errors in the output of the valve.

With the foregoing and still other objects in view, which will be apparent from the following description of our invention, our invention includes the novel correlation and relative arrangement of elements described below and illustrated in the accompanying drawings, in which:

Fig. l schematically represents a preferred embodiment of our invention, including the wiring diagram of the electrical elements illustrated therein;

Fig. 2 is a somewhat schematic, detailed illustration of one of the elements preferably embodied in the circuit of Fig. 1;

Fig. 3 schematically represents a modified form of automatic pilot;

Fig. 4 is a fragmentary, sectional elevational view of a mounting for a flux valve of one type, the flux valve being shown supported therein;

Fig. 5 is a view similar to Fig. 3 showing a second type of iluX valve supported in the mounting therefor and associated means for turning the lux valve in azimuth relative to the craft on which it is mounted; and

Fig. 6 is a somewhat schematic illustration of an automatic pilot generally similar to that illustrated in Fig. l, but somewhat modified and particularly showing the mechanical aspects of the pilot.

Preferably, in the present invention we employ a directional gyro which provides an azimuthal direction reference and means controlled by the position of the directional gyro for controlling the position of a control surface or the rudder of a dirigible craft. Since a gyro of the character herein employed does not continuously provide a predetermined directional reference but wanders therefrom, due to external forces acting thereon, we also employ a ux valve for slaving the gyro or causing it to return to a predetermined reference position if it should Wander therefrom. Broadly speaking, flux valves may be considered of twoY types, one which continuously provides signal voltage outputs which are proportional in magnitude to the component of the earths field lying along the legs thereof, while the other type is of such character that in one position thereof in the earths eld, no voltage output will be produced. The foregoing characteristics of these two types of valves must therefore be considered when utilized in an automatic pilot. When using the former type, Wherein voltage outputs are derived therefrom for all positions thereof' in azimuth in the earths eld and where the fluX valve is mounted to move in azimuth with the craft, some means must be provided to compensate or correct for azimuthal movement of the ilux valve when the directional gyro or its vertical ring remains stationary in space. When the latter type of ifux valve is employed, its zero voltage output position may be used as an azimuthal reference for the gyro, and the craft itself, through the operation of the automatic pilot, may serve to maintain the direc- -of an exciting coil and its associated core.

Referring first to Fig. 1 wherein we have illustrated a preferred embodiment of our automatic pilot, it will be observed that therein we illustrate a flux valve of the first type above described or one which will provide signal voltage outputs for all azimuthal positions thereof in the earths field. In Fig. l we have by way of example shown a three-legged flux valve, the core legs of which are radially arranged at equal angles to each other and are formed of permeable magnetic material. The flux valve indicated generally at I comprises the legs 2, 3 and Il, each of which is bifurcated at its inner end or at the geometric center of the valve as more clearly illustrated in Fig. 4. Each leg may comprise upper and lower laminations which extend in adjacent, superimposed relationship through-out the major lengths thereof, but are bent outwardly in opposite directions and thence over bent in spaced parallel relationship so that the respective laminations of each leg may be secured together at the center of the valve and to opposite ends Respective laminations of the core legs may be integral. The outer ends of the core legs may be provided with flux collectors 6 or horns. Upon each leg is mounted a pick-up coil l, 8 and 9 which may be Y-connected as shown to supply a plurality of output voltages in polyphase fashion.

As shown in Fig. 4, the flux valve is preferably pendulously m-ounted on the craft so as to maintain its average position horizontal. The flux valve is shown as enclosed in a liquidtight container I0, suspended on a universal connection II which, in turn, is supported in the top of the outer casing I2. The outer casing is adapted to be fil-led at least in part with a damping liquid such as oil and the ux valve and its enclosing casing I0 is rendered pendulous by a mass i3 secured -to the bottom of container Ill. Flexible wires may be employed to conduct current to the exciting coil of the flux valve and to connect the pick-upfcoils in which the signal voltages are generated with the circuit of the pilot. Container swing out on turns vor under other vaccelera-tion forces and we prefer to disconnect the flux valve from the gyro or to break the connections therebetween during such turns for reasons hereinafter particularly pointed out. Hence, as shown in Fig. 1,the output conductors I4, I5 and I6 are connected Ito a turn responsive circuit breaker, the output conductors Illa, 65a and isa of which -are connected with the polyphase winding of a signal transformer indicated generally at l'I.

The turn responsive circuit breaker may be of the character shown in Fig. 2 wherein a switch I8 serves normally to connect conductor i4, I5 and -I-6 with conductor Illa, IE and Ilia. A rate of turn or turn indicator type gyro I9 operates to open the switch I8 through the medium of the heart-shaped cam 29 and follower rod 2l which is normally biased to urge the switch I8 in circuit closing position by spring 22. Precession of the rate gyro in either direction about its axis will cause the cam to depress the follower rod 2l lto thereby disconnect the output leads of the flux valve from the input leads to the signal transformer Il.

`which `matured into Patent No. 2,383,459.

The leads I4a, IECL, and 96a, as hereinabove` described, are connected with the three windings constituting the polyphase winding 23 of the signal transformer Il. A single phase winding 2d of the transformer I1 is connected to a suitable phase sensitive amplifier 25. The windings of the polyphase winding 23 of the transformer are arranged in relative angular relationship forming equal angles therebetween and therefore provide a resultant magnetic field havving a ydirection corresponding to the direction of the earths field. The winding 23, in the embodiment herein illustrated is connected to rotate with the vertical shaft 26I of the vertical ring of the directional gyro 26, while the winding 24 -is relatively stationary or, in other words, fixed to move in azimuth with the craft. Of course, winding 24 could be mounted to rotate with thevertical ring of the gyro while the polyphasewinding is mounted to move in azimuth with the .craft. As long as the polyphase winding 23 occupies a certain relative angular position with re.- spect to winding 2.4 as compared to the position of' the piola-.up .coils l, 9 and 9 of the flux valve in theearths field no signal is generated in the winding .24, but upon relative displacement from the: .above assumed relative position between the: winding 2:3 and the iiux valve coils 1, 8 and 9,. an A. C. signal will be generated of one or the opposite phase in the single phase winding 24 of transformer I'I depending upon the direction of,v such ,dis-placement. This signal is employed to cause procession of the directional gyro 26 to y'bring it` into relative agreement with the directional reference provided by the flux valve. To this end, we have shown the signal from the wind-- ing 24 as led to a phase sensitive amplifier and thence to the precessing coils 21 and 28 of the directional gyro. For phase-sensing purposes, alternating current from the source 29 which is employed in exciting the flux valve is connected through a frequency doubler 39 and double-fre- V.quency energy is supplied to the amplifier as a reference frequency for phase-detection purposes. The necessity of employing a frequency `doubler, which may be of any suitable type, is because the signal voltage outputs of the flux valve -ivill 'be of a frequency equal to twice that of the exciting current as explained in the application of Lennox Beach, Serial No. 348,582, for ,Indi- ,cat or for Magnetic Fields, filed July 30, 1940, and The precessing coils are so connected with the output ,of the amplifier that when a signal is supplied to the amplifier of one phase representing a wandering-movement of the gyro in one direction, the coils will exert a torque causing the gyro to process back to the position from which it has wandered while a signal of the opposite phase, supplied to amplifier 25, will cause the precessing lcoils to ,exert-a torque in the opposite direction.

In'the embodiment herein illustrated, a signal generator, indicated generally at 3l, of the Selsyn type is employed as a pick-olf at the gyro. The generator 3l includes relatively movable, polyphase and single phase windings indicated generally at 32 and 33, one of which is mounted `to rotate with the craft in azimuth and rthe other of `which is positioned by the vertical ring of the gyro. In Fig. i, the single phase winding is mounted to rotate with the vertical ring of the gyro and is excited from a suitable source of alternating `current such as source 29. The polyphase winding, which is movable with the craft in azimuth, is connected through conto position a control surface or the rudder 43 of a dirigible craft.

The signal generator may be employed for course-setting purposes or to control the rate of turn of the craft and in Fig. l we have illustrated it primarily as arranged for course-setting purposes Whereas its connection for rate of turn control is shown to better advantage in Fig. 6. The course-setting knob 44 serves to position the polyphase winding 34 of the signal generator relative to the single phase winding 36 thereof and, as hereinafter described in connection with Fig. 6, gear meshing with worm 46 which, in turn, is driven through a suitable variable speed drive from a constant speed motor, is connected to rotate the single phase winding 36 for rate of turn `control purposes.

The operation of the embodiment of our present invention hereinabove described should be clearly evident from the following brief description thereof. As above indicated, the flux valve l is mounted upon and fixed to turn in azimuth with the craft. The directional gyro 26, however, may rotate about its vertical or azimuth axis relative to the craft as the craft turns and, of course,v

Under these condirelative to the flux valve. tions, assuming that the craft turns in azimuth or maintains a given heading while the gyro provides a predetermined orientation or error-free directional reference, the gyro should be free fromrany precessing torque. However, unless some compensating means were provided, the

turn of the flux valve with the craft in azimuth would institute the application of a precessing torque to the gyro due to the fact that the direction of the resultant field produced by the output voltages of the flux valve in the polyphase winding of the synchronous transformer I1 will change with azimuthal rotation of the flux valve and therefore a signal would be generated in the single phase winding 24 of the transformer. By

relatively rotating the windings 23 and 24 of the synchronous transformer I1, in accordance with turning of the craft and flux valve in azimuth,

, the electrical relationship of the windings is'preserved and does not vary when the flux valve only turns in azimuth, whereby no signal is supplied to cause operation of the gym-precessing means or coils 21 and 28, and therefore compensation for azimuthal rotation of the flux valve, alone, is accomplished. In the embodiment illustrated, the polyphase Winding 23 of the synchronous transformer moves in azimuth with the vertical ring ofthe gyro relative to winding 24 which moves `only in azimuth with the flux valve and the craft.

Hence, for all azimuthal movements of the flux valve, no operation of the gyro-precessing coils Vwill be effected unless the gyro wanders or deviates from its predetermined position of orientation. In this latter event, the electrical relationship of the windings of the synchronous transformer will vary and the gyro will be caused to .precess in a deviation-correcting direction.

,-,Fromthe foregoing it will be readily observed that-,the directional gyro 26 asso slaved by the :lux valve l will provide an azimuthal reference 6 f for controlling the course or heading of the dirigible craft and the course or heading will not vary so long as the electrical relationship between the polyphase and single phase windings of the pick-off 3l and signal generator 35 is preserved. If the craft should deviate from the course established by the directional gyro, Winding 32 of the pick-off 3l will rotate with the craft relative to the single phase Winding 33 thereof which is positioned by the directional gyro thereby'producing a signal of a phase sense depending upon the direction of relative rotation of the windings which is supplied through the signal generator 35 to the phase sensitive, rudder-servo amplifier causing the servo to actuate the rudder in a direction to restore the craft to its original heading. When it is desired to change course, the course-setting knob 44 may be rotated in one direction or the other thereby generating in the winding 36 thereof a signal voltage of one phase sense or the other depending on the direction of rotation of the polyphase winding relative thereto. This signal is supplied to the rudder servo amplifier causing the servo to operate the rudder in the direction and to a degree dependent upon the phase sense of the signal and the magnitude thereof. The signal, therefore, will cause the craft to turn until the polyphase Winding 32 of the pick-off 3|, which turns in azimuth with the craft, angularly shifts the direction of the resultant field of the polyphase Windingof the signal generator 35 to the same angular extent as the course-setting knob 44 has been rotated. In other words, the craft in response t0v a signal generated by the signal generator 35 will turn through an angle corresponding to the relative angular movement effected by the coursesetting knob between the windings 34 and 36 or until this signal is reduced to zero through the operation of the pick-off 3 I. i

In the form of our invention disclosed in Fig. 3 we employ a flux valve of the second type hereinabove referred to or, in other words, a flux valve which is characterizedby the fact that in one position thereof in azimuth it will provide zero voltage output. The flux valve indicated generally at 41 in Fig. 3 comprises a cruciform core 41a on the respective legs of which are mounted both exciting and pick-up windings. In the embodiment illustrated, each leg of the core is provided with a cut-out portion on opposite sides of which the exciting coils 48 are wound. These coils may be connected in series or parallel and connected through conductors4 49 to a suitable source of alternating current such as one phase of a three-phase source 50. The pick-up coils 5I, 52, 53 and y54 are mounted on the respective legs of the core, being connected in series and through conductors 55 to a circuit breaker 56.

Where the flux valve is employed as a component of an automatic pilot for use on aircraft, the flux valve 41 may be mounted as shown in Fig. 3, dependence being had on the automatic pilot to maintain the craft and the flux valve stable against roll and pitching. However, flux valve 41 may be mounted in pendulous fashion so as to maintain its average position horizontal as shown in Fig. 5. In Fig. 5, the ux valve 41 is enclosed in the liquid type container l0 of the character shown in Fig. 4 which is suspended on the universal connection Il from shaft 51 which is rotatably supported in the top of the outer casing l2. Casing I2, as hereinbefore pointed out, may be lled with a damping liquid and ux '7 valve and its casing In may be made pendulous `glyro 19. i character shown in our parent application above by mass 1 3. Flexible wires are `employed to con.- diict exciting Icurrent to the valve and to kconnect the pick-upicoils thereof ywith .the balance vof the pilot system. In the event the flux valve is pendulously supported it may be rotated in azimuth ,about the axis of shaft 5l by `means of gear '5 8 .secured 'to shaft 5l and meshing with worm 59 which may be suitably supported in a bearing` 60 lon the top of the outer casing l2.

In Fig. 3 rotation of the flux valve il in azimuth is similarly .accomplished through the medium of gear 6I and shaft 62, secured. thereto and to the flux valve 4l, and worm 53. In this embodiment of our invention the means *for dis,- connecting the flux valve from the gyroscope during turns is shown as circuit interrupter 56 Lwhioh includes a centrifugal device Eli connected to rotate `with the change-course shaft 65 of the automatic vpilot with which'worm .63 rotates. The circuit interrupter includes switches vi which are y:normally biasing to closed position, but upon rotation of the shaft 65 by means of a handle `or 4 knob 61, the centrifugal masses 68 fly out and rotate the bell .crank lever '59 temporarily to open the switches SE during the turn. The circuit interrupter is also connected through conductors l to amplifier 1I which, in turn is connected to the opposed coils l2, i3 of a polarized relay l, the polarizing winding being shown at l5; Winding 'L5 is shown as excited from the source of alternating current v5I] through any suitable form of frequency doubler ITB for the reasons hereinbefore `explained in connection with frequency doubler 3B. Excitation of the relay in one phase sense will cause armature 'd6 to engage contact A and in the other phase sense contact B, these contacts being connected to the A. C. torque device 11 ,mounted on thevertical ring 'i8 of lthe The torque motor 'l1 may be of the referred to, Serial No.,36.6,370 and may comprise, for example, .three windings which are preferably mounted on vertical Vring 8B land a squirrel A,cage rotor which Ais secured on the trunnon `8i which rotatably supports the rotor bearing `case 82 of thegyrofon the vertical ring. Two of the windings may be connected at one v end thereof respectively `to the contacts .A .andB of ,the relay 'Hand the other ends thereof may `be connected .together and to one .of the terminalsof the three `phase supply .59, the contacts A and B serving .to connect these windings across -one phase ,of the .three-phase supply. The third winding may be connected directly acrossy another .phase of said supplyso that the device operates as a two phase,

reversible induction motor.

I 'ln this embodiment 4of our invention, the rudder servo is controlled by a relay 8 3 which, in turn, is'controlled by a suitable Apick-off `84 at the directional gyroscope. The `servo motor, of course, may likewise .be controlled in the manner illusmated in Fig. 1. The pick-off sa .is illustrated as of the well known inductive type comprising a three-fingered or E transformer 8ia, Ynfiountecl `on the follow-up ,disc 85, land a movable core 86 rsecured to the shaft .ii-"l which, in turn, is connected to rotate in azimuth with the vvertical ring t0 of gyroscope 1.9. Disc 85 is shown fas mounted on a shaft 8B which may lbe turned from the course change knob Si through shaft 55, worm 39 and lworm wheel v20 so that course changes may be simultaneously made in one operation on both the directional gyroscope and the 1111K valve. Gears V9| and 92, as shown, impart motion to the Vcentrifugal device 64 when the .course-change knob B7 is rotated.

In this embodiment, a simple or one-way oo nnection may be employed between the flux valve Alil and the gyroscope 'I9 since the follow-back connection, in this instance, is furnished by the air craft itself, the heading of which is `automatically controlled from the gyroscope 79.

The operation of the modification of our invention shown in Fig. 3 briefly is as follows. Assuming that the flux valve 48 liesin the .position Iin which it provides zero signal voltage output, the gyroscope i9 providing a directional reference, if the pick-ofi 84 supplies no Asignal -to relay 33, the heading of the craft will not be in error rand no actuation of lthe control surface .or rudder o f the craft-will take place. Upon change of course due to actuation of Jthe knob 6l, caiising lrelative movement `between the armature and core of the pick-off 8d, a signal will be supplied to relay 83, causing' the servo motor -to actuate the control surface in a direction to place the craft von a new heading. Simultaneously with relative angular vmovement of the parts of the pick-off, by the knob lEil, the flux valve Iii will be rotated in azimuth through a similar angular extent, and the craft, when it moves through the same angle to follow its new heading, will carry the flux valve therewith and back to a zero voltage output position. Should the gyro wander, such movement thereof will provide a signal voltage output lfrom pick-off 84 causing the craft to follow a heading corresponding to the change in the reference caused by the wandering of the gyro. Such change in heading of the craft will move the flux valve to `a position wherein a signal Voltage will be supplied to the amplifier and its associated relay 14, thereby causing a precessing torque to be applied to the gyro in such a direction as to move the gyro in Yazimuth back to the position from which ithas wandered. The craft, of course, will follow the precessing movements of the gyro 'and will thereby be returned to its original correct headlng.

While vin the drawings we have shown the flux valve `as lmounted independently of and remote from the directional gyroscope, the flux valve may, if desired, be mounted directly on the gyroscope and stabilized thereby. In this event, we prefer Vto mount the flux valve on the rotor bearing' case 82 of the gyroscope so that the flux valve will vbe stabilized at least about the horizontal trunnion 8l and, preferably, these trunnions normally extend in a north-south direction so that the vertical axis of the flux valve is not vtilted out -of the vertical plane containing said axis.

In the modifications of our invention illustrated in Figs. l and 3, it will be observed that .we have illustrated the preferable inclusion of `circuit-interrupting means between the flux valve and the ygyroscope. The purpose of a `means kof this character is -to temporarily remove the fiux valve control over the gyro-precessing `means during turning movements of the valve and craft. In automatic pilots of the character contemplated in the present invention and as illustrated in Fig. 6, means are provided for controlling the rate of turn of the craft and for insuring' a correct bank angle during such turns. If the turns under these conditions are of considerable duration, errors may creep in if the flux valve were connected in controlling relation to 'the gyro during such turns. Turning of the craftwill cause the pendulously supported flux valve to v,swing out of the horizontal plane it normally would disturb the signal equilibrium existing in the control circuits of the automatic pilot during turns and while the craft is turning at the correct prescribed rate and corresponding bank angle as hereinafter pointed out. Therefore, we prefer to remove the control of the flux valve over the gyro during such turning movements. The following description of Fig. 6` will bring out more clearly the function of our preferred form of an automatic pilot in controlling the craft as described in the foregoing.

In the embodiment of our invention illustrated in Fig. 6, we have shown a pair of valves indicated generally at d3 and 94, respectively, which are adapted to be pivotally supported on the craft in spaced relation to each other and on opposite sides of the yaw axis as, for example, in opposite wing tips of the plane.

Ordinarily, in a straight line course of the craft, the pendulously supported fiux valve would be maintained substantially in a horizontal plane. However, since they are pendulous, they are subject to acceleration or deceleration forces and may oscillate about the true vertical. lf these oscillations are symmetrical and of a fairly short period, a directional gyro will act as an averaging or integrating device and its directional indication will remain accurate. When used in aircraft, it is desirable to place the iiux valve remote from the gyroscope and from the cabin of the plane as in the wing tip in order to avoid magnetic interaction with instruments, controls, engine parts, and the armor of the fuselage if such is used. When the iiux valve is pendulously supported in a wing tip it is subjected to various forms of acceleration forces. One force most seriously effecting the flux valve is that experienced while the ship is yawing since this type of acceleration has a fairly large period and its-effect will not be averaged out. In yawing one wing of the craft accelerates to a position ahead of the other during one-half cycle and will then decelerate while the other wing accelerates.

However, by mounting a pendulously supported fiux valve in one wing and another in the other wing, or on opposite sides of the yaw axis of the craft, both flux valves will be tilted outwardly during yaw resulting, for example, in a forward and left tilt for one and a rearward and right tilt for the other. In other words, the angular tilt of each flux valve will be approximately equal and opposite to that of the other one. As a result, for a reasonably small amplitude of oscillation, any spurious error or change in signal of one flux valve will be compensated for by a similar error in the other one so that average instantaneous combining of the signais of the two flux valves will provide a more accurate indication of the true magnetic bearing.

Therefore, in Fig. 6, we have shown two pendulously supported flux valves which are adapted to be mounted on a craft on opposite sides of the yaw axis thereof or in opposite wing tips of a plane, the exciting windings thereof being ener'- gized from'the alternating source 2c. The flux valves may be of the character illustrated in Fig. l with corresponding legs having like orientations in the earths field, the outputs of the pick-up windings of corresponding legs being connected together by conductors 95 in such a manner that the respective voltage outputs are added together for normal flux valve operation. However, the spurious error outputs will oppose each other for the reasons advanced in the above. The arrangement cf the flux valves as described will also compensate at least in part for the effect thereon of distortion of the magnetic eld in the vicinity of the craft because of the large masses of iron or other magnetic materials in or around the fuselage. The effect of these magnetic masses is to produce static deviation errors which are at least partly balanced out by the use of two flux valves arranged in the manner above described.

The flux valves are connected from the crossconnecting conductors 95 through conductors 5S to the signal transformer Il which is associated with the directional gyro 2% as hereinabove described in connection with Fig. l. In this em'- bodiment of our invention we have not included the circuit-interrupting means hereinbefore described, but it is to be understood that such means may be included as disclosed in Fig. l. The illustration in Fig. 6 of the gyroscope 26 and its associated control elements and pick-off are similar in all respects to that shown in Fig. l and a detailed description thereof at this point is deemed unnecessary save to point out that the gyroscope shown in Fig. 6 is provided with a vertical reading compass card 91 driven from the vertical ring 9S of the gyro through bevel gears 9S and lili). The processing coils 2l and 28 are as hereinbefore described in connection with Fig. l, and permanent magnets I6! fastened to the rotor bearing case cooperate therewith in producing a torque to cause precession of the gyro about its vertical or azimuth axis.

In Fig. 6, the output of the pick-off 3i is supplied to the signal generator 35 as hereinbefore described and the output of the signal generator is supplied as the phase-sensitive servo amplifiers 38, the output of which actuates torque motor 4U. In the illustration of the present embodiment of the invention, we have shown a servo motor of the hydraulic type, the armature 4t2 of the torque motor serves to actuate the rocker arm H33 of a pilot valve which controls the operation of the servo. When using a hydraulic servo, we prefer to use one in which the aerodynamic forces acting on the control surface or rudder 43 will react through the connections between the rudder and servo and through the fluid of the system as a repeat back to the pilot valve, whereby displacement of the control surface will be measured against the magnitude of the control signal sup-plied to the servo amplifier.

In Fig. 6, we have illustrated a suitable form of mechanism for effecting a rate of turn control over the craft. The polyphase winding of the signal generator 35 may be displaced relative to the single phase winding thereof by means of course-setting knob 44 as hereinbefore described in connection with Fig. 1. For rate of turn control purposes, the single phase winding 36 of generator 35 may be angularly displaced relative to the polyphase winding thereof at a desired rate. For this purpose, we have shown a constant speed motor |64 which drives through a suitable worm |05 and meshing worm wheel ISES,

worm I? and meshing worm wheel H18, to the disc H99 of a variable speed transmission. A ball carriage i l@ is interposed in frictional engagement With the disc M9 and cylinder I IQ and the position of the ball carriage measured radially of the disc H39 will determine the rate of the output of the variable speed transmission or the rate at which worm i6 is rotated. A turn control knob H2 serves through the medium of bevel gears H3, shaft IM, gear H5 and rack H6 on which the ball carriage is mounted to control the radial position of the ball carriage and the rate at which angular displacement between the single phase winding 36 and the polyphase winding 34 of the signal generator occurs.

With the arrangement shown in Fig. 6, the degree and direction of angular displacement of the turn control knob I l2 will control the rate and the phase sense of change of signal output from the signal generator 35, and the automatic pilot will actuate the control surface of the craft to initiate a rate of turn of the craft corresponding to the rate of turn set in by the turn control knob H2 or until the rate signal derived from the signal generator 35 is substantially matched l.

by a similar signal supplied from the pick-olf 3l. The signal from 3l, 0f course, will be dependent upon the rate of turn of the craft since the single phase winding 33 of the pick-off will remain stationary in space with the vertical ring of the gyro and the polyphase winding 32 thereof will rotate with the craft in azimuth.

Turn control knob l l2 may also operate to control a potentiometer l il or other suitable signal generator which serves to supply a signal for aileron control purposes, the signal being supplied through a suitable amplifier in controlling relation to a servo which operates the ailerons of the craft as shown. Hence, a control over both the rudder and ailerons may be exercised for turning the craft at a desired rate of turn. rlhe rudder initiates the turn and thereafter may assume a neutral position while the craft is turning at the prescribed rate. Under these latter conditions, the signal supplied to the rudder servo Iamplifier is substantially reduced to zero through the operations of pick-off 3| and signal generator 35. Hence, as hereinbefore described, during turns, precession of the gyro due to spurious error voltage outputs of the llux valve or valves is not r desirable since such operation would change the output of the pick-off 3l, thereby affecting an otherwise correct attitude and bank of the craft while turning at the prescribed rate.

Since many changes could be made in the above construction and many apparently Widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1`. An automatic pilot for positioning a control surface of a craft comprising aiiuX valve adapted to provide a signal output varying with changes in azimuthal position of said valve, a directional gyro movableV in azimuth relative to said valve, means for precessing said gyro about its azimuth axis, electrical means controlled by said 'ux valve for controlling saidv precessing meansand including a signall responsive means for receiving` the output from said flux valve and means for compensating for any change in the received output from said valve when azimuthal rotation Only of said valve occurs, and means responsive to the azimuthal position of said gyro for controlling the position of said control surface.

2. An automatic pilot for positioning a. control surface of a craft comprising a flux valve, a directional gyro movable in azimuth relative to said valve, means for precessing said gyro about its azimuth axis, electrical means controlled by said flux valve forv controlling said precessing' means and including a 'pair of electrically cooperable, relatively movable elements, one ofv said elements being movable in azimuth with said flux valve and the position of the other element being controlled by said gyro to correspond with the azimuth position of said gyro, and one thereof being responsive to the signal output of said valve and the other being operable to supply a voltage output and thereby effect an operation of said gyro precessing means when the electrical relationship of said elements varies from a predetermined one providing substantially zero voltage output, a servomotor for Ipositioning said control surface, pick-off means at said gyro, and means responsive to the signal output of said pick-off means for controlling said servomotor.

3. An automatic pilot for positioning a control surface of a craft comprising a flux valve, a directional gyro, means for precessing said gyro about its azimuth axis, control means for said precessing means including a self-synchronous transformer having two relatively movable windings, a first of said windings being connected to receive the output from said flux valve and one being fixed against azimuthal rotation relative to said flux valve and the other winding being movable relative thereto with azimuthal rotation of said gyro whereby a control signal is generated in a second. of said windings when a departure of said .gyro from a predetermined azimuthal position occurs, a servomotor for actuating said control surface, pick-off means at said gyro, and means responsive to the signal output of said pick-oit means for controlling said servomotor.

4. An automatic pilot for positioning a control surface of a craft comprising a flux valve adapted to provide a signal output varying with changes in azimuthal position of said valve, a directional gyro movable in azimuth relative to said valve, means for precessing said gyro about its azimuth axis, electrical means controlled by said flux valve for controlling said precessing means and including a signal responsive means for receiving the output from said flux valve and means for compensating for any change in the received output from said valve when azimuthal rotation only of said valve occurs, a servomotor for actuating said control surface, pick-off means at said gyro for providing a signal output when the heading of said craft and the directional reference provided by said gyro changes, means responsive to the signal provided by said pick-off for controlling said servo, and means for further controlling the pick-off signal supplied to said last-mentioned means.

5. An automatic pilot for positioning a control surface of a craft comprising a ilux valve adapted to provide a signal output varying with changes in azimuthal position of said valve, a directional gyro movable in azimuth relative to said valve, means for precessing said gyro about its azimuth axis, electrical means controlled by said flux valve for controlling said precessing means and including a signal responsive means for receiving the output from said iiuX valve and means for compensating for any change in the received outputfrom said valve when azimuthal` rotation only of said valve occurs, a servomotor for actuating said control surface, means controlled by the'position of said gyro including course-setting means for controlling said servo in accordance with the directional reference provided by said gyro and said course setting means.

6. An automatic pilot for positioning a control surface of a craft comprising a uX valve, a directional gyro, means for processing said gyro about its azimuth axis, control means for said precessing means including a self-synchronous transformer having two relatively movable windings, a rst of said windings being connected to receive the output from said flux valve and one being fixed against azimuthal rotation relative to saidflux valve and the other winding being movablerelative thereto with azimuthal rotation of said gyro whereby a control signal is generated in a second of said windings when a departure of said gyro from a predetermined azimuthal position occurs, a servomotor for actuating said `control surface, and electrical means associated with said gyro and servo including course-setting means for controlling said servo in accordance with the4 directional reference provided by said gyro and said course-setting means.

7. An automatic pilot for positioning a control surface of a craft comprising a flux valve adapted to provide a signal output varying with changes in azimuthal position of said valve, a directional gyro, means for processing said gyro in azimuth, electrical means controlled by said flux valve for controlling said precessing means including a signal responsive means for receiving the output from said iiux valve and means for compensating for any change in the received output from said valve when azimuthal rotation only of said valve occurs, a servomotor for positioning said control surface, a first signal-providing means actuated by said gyro when relative azimuthal movement of said gyro and craft occurs for supplying a signal to control said servo, a second signalproviding means for supplying a servo-controlling signal proportional to a desired rate of turn of said craft, said first and second signal-providing means being so constructed and arranged that zero signal is supplied when the desired rate and actual rate of turn of the craft are equal, and means for removing the control of said flux valve over said gyro-processing means during turning movements of the craft.

3. An automatic pilot of the character recited in claim 7 in which the flux valve is pendulously supported.

9. In an automatic pilot of the gyro-magnetic type for positioning the rudder of a craft, a magnetic device for providing an azimuth reference through interaction with the earths magnetic field, a directional gyro, means for precessing said gyro in azimuth, electrical means for controlling said precessing means including means responsive to change in position in azimuth of said directional gyroscope with respect to the earths magnetic field as determined by said magnetic device, a servo motor for positioning said rudder, a first signal-providing means actuated by said gyro when relative azimuthal movement of said gyro and craft occurs, and a second signal-providing means for supplying a signal proportional to a desired rate of turn of the craft, said two signal-providing means being so constructed and arranged that a zero signal is supplied to control said servo .motor when the desired rate of turn and the actual rate of turn of the craft are equal.

10. In an automatic pilot of the gyro-magnetic type for positioning the rudder of a craft, a magnetic device for providing an azimuth reference through interaction with the earths magnetic field, a directional gyro, means for precessing said gyro in azimuth, electrical means for controlling said processing means including means responsive to change in position in azimuth of said directional gyroscope with respect to the earths magnetic field as determined by said magnetic device, a servomotor for positioning said rudder, a rst signal-providing means actuated by said gyro when relative azimuthal movement of said gyro and craft occurs, a second signal-providing means for supplying a signal proportional to a desired rate of turn of the craft, said two signal-providing means being so constructed and arranged that a zero signal is supplied to control said servomotor when the desired rate and theactual turn of the craft are equal, and means for removing the control of said magnetic device over said gyro processing means during turns of the craft.

l1. An automatic pilot for positioning a control surface ofla craft comprising a flux valve adapted to provide a signal output varying with changes in azimuthal position of said valve, a directional gyro, means for processing said gyro in azimuth, electrical means controlled by said ux valve for controlling said precessing means including a signal responsive means for receivy ing the output from said flux valve and means for compensating for any change in the received output from said valve when azimuthal rotation'only of said valve occurs, a servomotor for positioning said control surface, a rst signal-providing means actuated by said gyro when relative azimuthal movement of said gyro and craft occurs for supplying a signal to control said servo, and a second signal-providing means for supplying a servo-controlling signal proportional to a desired rate of turn of said craft, said first and second signal-providing means being so constructed and arranged that zero signal is supplied when the desired rate and actual rate of turn of the craft are equal.

12. In an automatic pilot of the gyro-magnetic type for positioning a control surface of a craft for controlling azimuthal movements of said craft, a magnetic device for providing an azimuth reference through interaction with the earths magnetic field, a directional gyro, means for precessing said gyro in azimuth, electrical means for controlling said processing means including means responsive to change in position in azimuth of said directional gyroscope with respect to the earths magnetic eld as determined by said magnetic device, a servomotor for positioning said control surface, a rst signal-providing means actuated by said gyro when relative azimuthal movement of said gyro and craft occurs, and a second signal-providing means for supplying a signal proportional to a desired rate of turn of the craft, said two signal-providing means being so constructed and arranged that a zero signal is supplied to control said servo motor when the desired rate of turn and the actual rate of turn of the craft are equal.

13. An automatic pilot for positioning the rudder of a craft, comprising an inductive device having a multipolar stator winding, and a rotor having a winding, a directional gyroscope connected to orient said rotor, a source of single phase current, a magnetic device adapted to provideY anV azimuth reference through interaction withv the earths magnetic eld. and. including a stationaryy multipolar Winding electrically-com nec'ted tothe multipolar winding of said inductive device; and a. stationary winding electrically connected to said source, a winding for. applying a torque about. the horizontal axis of said directional gyroscope, a` phase-sensitive controller' electrically connected to. said rotor winding for supplying reversible D, C., to energize said torque winding only upon departure of the directional gyroscope from itsr predetermine d orientation inthe earths eld, means for generating a` signal. upon cha-nge of. heading of the craft with respect to. said directional gyroscope and a servomotor controlled .by saidL signal for. turningYA said rudder to restorer the craft to its original heading,

1'4.` An automatic pilot for positioning the rudder of a craft, comprising a signal transformer having1 a` polycircuit stator Winding anda rotor Winding, a magnetic device for providing an azimuth reference through interaction, with the earths magnetic eld andv including an exciting winding and a polycircuit winding for providing anoutput varying with variations in the posi tion of ther earths eld relative thereto, the polycircuitwindings of said` device4 and transformer being connected, together in polycircuit.

fashion whereby the direction of the resultant field in said transformer depends upon the direction of the earths eld relative to saidk mag netic device, a directional gyroscope connected to orient` said rotor Winding, a Winding for slaving said directional gyroscope, a phase-sensitive controller controlled by the output of said rotor winding to energize said slavingwinding, a transmitter oriented by said gyroscope and a servomotor connected to said rudder and controlled from said transmitter.

ORLAND E. ESVAL.

CARL A. FRISCHE.

REFERENCES CITED The following references are oi record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,863,415 Rieber June 14, 1932 1,958,259 Becker May 8, 1934 2,115,498 Rieper Apr. 26, 1938 2,126,855 Wunsch et al Aug. 16, 1938 2,177,242 Carlson Oct. 24, 1939 2,308,566 Noxon Jan. 19, 1943 2,313,682 Stuart Mar. 9, 1943` 

